气体继电器及其二次回路试验时,整定值符合运行规程要求,动作正确,绝缘电阻一般不低于()。
A.0.5MΩ
B.1MΩ
C.1.5MΩ
D.2MΩ
参考答案:B
根据视屏信号的高频调制方式不同,目前世界上有()、()、SECAM三种。
— John failed his final exam.
— I'm not surprised at the news ______. ______, he is never seen busy with his lessons. [ ]
A. at all, After all
B. in all, After all
C. above all, In all
D. at all, In all